After last year’s “Last Christmas,” which featured Nick Frost as Santa Claus, Whovians have been wondering who this year’s guest star would be. Now we know.

Alex Kingston, who made her first Doctor Who appearance as time traveler Professor River Song in the 2008 two-parter “Silence in the Library” and “Forest of the Dead” and has appeared in 15 episodes to date.

When she returns to Doctor Who this Christmas, River Song meets her husband’s new incarnation, in the form of Peter Capaldi, for the first time on a Christmas Day in the future, when the TARDIS is parked on a snowy village street, covered in icicles, awaiting its next adventure.

Said the award-winning Kingston, “To be honest, I did not know whether River would ever return to the show, but here she is, back with the Doctor for the Christmas special. Steven Moffat is on glittering form, giving us an episode filled with humor and surprise guest castings. I met Peter for the first time at Monday’s read-through, we had a laugh, and I am now excited and ready to start filming with him and the Doctor Who team. Christmas in September? Why not!”

Showrunner, executive producer, and lead writer Steven Moffat added, “Another Christmas, another special for Doctor Who – and what could be more special than the return of Alex Kingston as Professor River Song. The last time the Doctor saw her she was a ghost. The first time he met her, she died. So how can he be seeing her again? As ever, with the most complicated relationship in the universe, it’s a matter of time …”

Additional guest stars joining Alex for this magical adventure on the TARDIS will be announced over the coming months.

Written by Steven Moffat, produced by Nikki Wilson, and directed by Douglas Mackinnon (Doctor Who, Sherlock), the eleventh Doctor Who Christmas special begins filming this week.

Doctor Who: Season 9 returns to BBC America on Saturday, 19 September 2015, with a 12-episode season, followed by the Christmas special on Friday, 25 December 2015.